Hi Maria,

One comment inlined #Keyur

From: GROW <[email protected]> on behalf of Robert Raszuk 
<[email protected]>
Date: Monday, April 1, 2019 at 9:31 AM
To: Maria Matějka <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [GROW] Prefix limit ORF: add grace time
Resent-From: <[email protected]>

Hi Maria,

So your suggestion is not to apply this limit at all (ie. have unlimited 
transient) - don't you think that in such a case your weakest network elements 
may just crash if say they expect 10 and will get 700K prefixes ?

I think what you are asking for can be easily achieved today during described 
migration if you adjust the prefix limit to some controlled higher value before 
your planned policy change then simply revert it back. Seems like very safe and 
problem free operation.

#Keyur: I agree with Robert. Wouldn’t it be simpler to simply have a higher 
prefix limit value that can accommodate the changes you describe?

Regards,
Keyur


Many thx,
R.

On Mon, Apr 1, 2019 at 5:29 PM Maria Matějka 
<[email protected]<mailto:[email protected]>> wrote:
Hello!

I'd like to suggest adding a grace time to the Prefix Limit ORF-Type.
Its purpose is to allow temporary overrun of the limit while reloading
the routes after a policy is changed.

Why: If the peer exports e.g. 2001:db8:0/48 through 2001:db8:7/48 and
it wants to substitute them for 2001:db8:0/45, it first has to add the
less specific prefix and then drop the more specific prefixes. Doing this
on large scale may override the limits temporarily which would lead to
unneeded BGP session drop.

Here are the changes to be done to the RFC text:

* append to section 3:
        The "Grace-Time" is a two-byte unsigned integer. It indicates
        the number of seconds for which the Prefix-Limit can be exceeded.

* append to section 4 the Grace-Time directly after the Prefix-Limit

* insert to section 6.1.1 after 2nd paragraph:
        The sending speaker MUST wait for the Grace-Time period before
        taking corrective action. If the peer gets from the Prefix-Limit
        violation during the Grace-Time period, no corrective action is taken.
        The Grace-Time period is reset every time the violation is gone.

Thank you for cnnsidering my suggestion
Maria

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